A cuckold is, quite simply, a man with an unfaithful wife. There are connotations of helplessness and humiliation attributed to the word, implications that the husband is helpless to stop her infidelity, and too cowardly to leave the wife. "Cuckold" appears in older texts as a highly insulting and pejorative term.

Cuckolds are sometimes written of as "wearing the horns of a cuckold" or just "wearing the horns". This goes back to an unsubstantiated reference to a tradition in villages of unknown European location where the community gathers to collectively humiliate a man whose wife gives birth to a child recognizably not his own. This is said to have been a parade where the hapless husband is forced to wear antlers on his head as a symbol of his wifes infidelity. Whether this actually happened or not is irrelevant to the phrase, which survived.

The history of the word is thought to be related to the Cuckoo bird, who is known to put its eggs in another bird's nest. Some think that this points to another hallmark of the cuckold  the raising of a child that is not his own.

Today the term is making a resurgence amongst non-monogamous couples with a dominant female allowed to take on additional partners, and submissive male who is not.

my carpool buddy and i were discussing this word today. its etymology is especially interesting- those no-good whoring birds!